Symmetry and topology are two of the main themes of modern physics, especially the condensed matter physics in recent decades. In two dimensions (2D), quantum (anomalous) Hall effects emerge with nontrivial electronic topology when the time-reversal symmetry is broken[1]}. When the time-reversal symmetry is preserved, quantum Hall states then develop into the quantum spin Hall (QSH) phase[2]}, [3]}. In three dimensions (3D), stacked QSH states evolve into topological insulators (TIs)[4]}, [5]}, [6]}. The crystal symmetries further intertwine with the electronic topology, leading to topological crystalline insulators[7]}, [8]}, [9]}.
These topological insulating phases have been experimentally verified with high precision in several materials, in particular highly efficient thermoelectric materials Bi\(_2\) Te\(_3\)  and Bi\(_2\) Se\(_3\)  and their alloy Bi\(_{2}\) Te\(_{3-x}\) Se\(_{x}\)[6]}, [11]}, [12]}, [13]}, [14]}, [15]}, [16]}.
Importantly, such TI materials have also been found to be intrinsically superconducting by the application of pressure[17]}, [18]}, [19]} or chemical dopant[20]}, [21]}, [22]}, [23]}, [24]}, which naturally invites two questions on the nature of this kind of superconductivity. From the symmetry wise, one needs to determine the pairing symmetry of the intrinsic superconductivity. From the topology wise, one needs to know whether and how the topological superconductivity can be realized in these topologically nontrivial materials.
